PSI - Issue 66

6

Umberto De Maio et al. / Procedia Structural Integrity 66 (2024) 459–470 Author name / Structural Integrity Procedia 00 (2025) 000–000

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The beam element has been discretized using 2D three-node triangular elements arranged in a Delaunay tessellation, used to discretize the bulk phase and 1D two node-elements used for longitudinal bars and shear stirrups.

Fig. 1. Geometric configuration, loading and boundary conditions of the beam model (all dimensions are expressed in mm).

3.2. Static analysis Preliminary, the proposed model has been validated by a comparison with experimental results proposed by (Hamad et al., 2015), carrying out a static displacement-controlled analysis. Numerical simulations have been conducted constantly increasing the displacements of the identified point on the upper edge of the mid-span section. The load versus mid-span deflection curve obtained through the proposed model, presented in Fig.2, highlights a good agreement with the experimental results (Hamad et al., 2015) and numerical ones (Pranno et al., 2022) taken from the literature. From the presented graph, it can be noted an increasing stiffness degradation as the damage level increases, and a trilinear behavior of the structural static response of the reinforced concrete beam.

Fig. 2. The load versus mid-span deflection curve and comparison with experimental (Hamad et al., 2015) and numerical results (Pranno et al., 2022) .

Subsequently, to analyze the structural behavior of the reinforced concrete beam under the action of loading and unloading cycles, nine damage levels (from L1 to L9) have been defined. As one can see in Fig. 3, at the end of the unloading phase, for each damage level, it is exhibited a residual plastic deformation, which is greater as the damage level increases. For high values of damage (from L6 to L9) two different slopes have been observed. They are related